Tunable sensing device

ABSTRACT

A tunable sensing device includes a substrate, a deformable dielectric unit and a tunable member. The dielectric unit is disposed on the substrate and is formed with a receiving space. The tunable member is received in the receiving space and has a stiffness tunable by an external electric field or an external magnetic field.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority of Taiwanese Patent Application No. 104134230, filed on Oct. 19, 2015.

FIELD

The disclosure relates to a tunable sensing device, more particularly to a tunable sensing device including a tunable member that has a stiffness tunable by an external electric field or an external magnetic field.

BACKGROUND

A conventional sensing device is able to convert physical quantities generated by an external force into measurable signals, so that it is possible to identify the interaction between the sensing device and the external force. Sensing devices, e.g., touch sensors or triaxial accelerometers are widely used in fields including robotics, gaming entertainment, biomedical technologies, etc.

In regards to touch sensors, measurable signals can typically be classified as piezoresistance, piezoelectricity, capacitance, or optical signals. In the case of capacitive sensing technology, a capacitive touch sensor includes a dielectric member sandwiched between two metal plates. According to the inverse relationship between distance and capacitance of the two metal plates, an external pressing force that causes decreased distance and increased capacitance between the metal plates allows for sensing of the external force dimensions.

Currently available capacitive touch sensors frequently employ the use of dielectric polymers such as polydimethylsiloxane (PDMS) to serve as the dielectric member. However, the fixed properties of the dielectric polymer cause capacitive touch sensors to have a fixed sensing range. Sensing ranges of these capacitive touch sensors can vary by adjusting the degree of crosslinking of PDMS (achieved by changing the proportion of curing agents used in formation of PDMS), which gives the dielectric member varying levels of stiffness and changes the sensing range of the capacitive touch sensor. In other words, when wishing to change the sensing range of currently available touch sensors, the dielectric member must be replaced, leading to reduced flexibility and limited sensing range associated with the existing touch sensors.

SUMMARY

Therefore, an object of the present disclosure is to provide a tunable sensing device that can alleviate the drawback associated with the prior art.

According to the present disclosure, a tunable sensing device includes a substrate, a deformable dielectric unit and a tunable member. The dielectric unit is disposed on the substrate, and is formed with a receiving space. The tunable member is received in the receiving space, and has a stiffness tunable by an external electric field or an external magnetic field.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the present disclosure will become apparent in the following detailed description of the embodiment with reference to the accompanying drawings, of which:

FIG. 1 is a partly cross-sectional view of an embodiment of a tunable sensing device according to the present disclosure;

FIG. 2 is a schematic view showing an external force applied to the embodiment;

FIG. 3 is a schematic view showing the external force applied to the embodiment, and an external electric field applied to a tunable member of the embodiment;

FIG. 4 is a diagram showing capacitance values of the embodiment versus values of the external force under different external electric fields; and

FIG. 5 is a schematic view showing the embodiment applied in a triaxial accelerometer.

DETAILED DESCRIPTION

Referring to FIG. 1, an embodiment of a tunable sensing device 1 according to the present disclosure includes a substrate 2, a deformable dielectric unit 3, a tunable member 4, and an electrode unit 5.

The dielectric unit 3 is disposed on the substrate 2 and is formed with a receiving space 35, in which the tunable member 4 is received. The dielectric unit 3 has a bottom portion 31 that is disposed on the substrate 2, a side portion 32 that extends from a periphery of the bottom portion 31 away from the substrate 2, and a top portion 33 that is connected to the side portion 32 and opposite to the bottom portion 31. The bottom portion 31, the side portion 32 and the top portion 33 cooperatively define the receiving space 35. The dielectric unit 3 further has at least one through hole 34. In this embodiment, the dielectric unit 3 has two through holes 34 that penetrate through the top portion 33, and that are in spatial communication with the receiving space 35. Moreover, the dielectric unit 3 includes a covering layer 36 that is disposed on the top portion 33 and that covers the through holes 34.

The electrode unit 5 includes a first electrode 51 and a second electrode 52, which are disposed in the dielectric unit 3, and are respectively disposed at two opposite sides of the tunable member 4. To be more specific, the first electrode 51 is disposed in the top portion 33 of the dielectric unit 3, and the second electrode is disposed in the bottom portion 31 of the dielectric unit 3. In certain embodiments, the top portion 33 of the dielectric unit 3 is formed with a recess 331 in which the second electrode 52 is disposed, and the second electrode 52 may be spaced apart from or in contact with the tunable member 4. Likewise, the first electrode 51 may be spaced apart from or in contact with the tunable member 4. The through holes 34 are respectively located at two opposite sides of the recess 311. In certain embodiments, the covering layer 36 contacts and covers the second electrode 52, such that the reliability of the tunable sensing device 1 is improved. It should be particularly pointed out that the position of the first and second electrodes 51, 52 may be changed as long as the first and second electrodes 51, 52 are respectively disposed at two opposite sides of the tunable member 4.

Specifically, the tunable member 4 enters the receiving space 35 through the through holes 34, after which the through holes 34 are sealed with the covering layer 36, such that the tunable member 4 is sealed in the receiving space 35. The number and the location of the through holes 34 are not limited to what is disclosed herein, as long as the tunable member 4 is capable of being disposed in the receiving space 35 through the through holes 34. In certain embodiments, the top portion 33 of the dielectric unit 3 may be omitted, and the covering layer 36 seals the receiving space 35 after the tunable member 4 is disposed in the receiving space 35. The second electrode 52 is disposed on the covering layer 36 opposite to the tunable member 4.

The tunable member 4 has a stiffness that is tunable by an external electric field or an external magnetic field. In certain embodiments, the tunable member 4 is a smart fluid, e.g., an electrorheological fluid (ER-fluid) or a magnetorheological fluid (MR-fluid), and includes an insulating fluid 41 and a plurality of particles 42 dispersed in the insulating fluid 41. The insulating fluid 41 may be silicone oil or mineral oil that have superior corrosion resistance, stability, insulativity (i.e., low electrical conductivity) and non magnetism, as well as low permeability. When the tunable member 4 is the ER-fluid, the particles 42 may be dielectric particles (e.g., silicon dioxide particles) that are capable of being polarized by the external electric field, and aligning along the external electric field for increasing the stiffness of the tunable member 4. When the tunable member 4 is the MR-fluid, the particles 42 may be magnetic particles (e.g., iron powders) that are capable of being polarized by the external magnetic field, and aligning along the external magnetic field for increasing the stiffness of the tunable member 4. In certain embodiment, the tunable member 4 is an electroactive polymer.

The substrate 2 may be made of silicon. The dielectric unit 3 may be made of a dielectric material, such as silicon dioxide (SiO₂), silicon nitride (Si₃N₄) polydimethylsiloxane (PDMS), etc. The covering layer 36 is made of a material selected from the group consisting of Parylene C, Parylene D, Parylene N, silicon dioxide, silicon nitride, polyimide, metal, and combinations thereof.

In certain embodiments, the substrate 2 is made of silicon, the dielectric unit 3 is made of silicon dioxide, the tunable member 4 is the ER-fluid, and the covering layer 36 is made of parylene C. The tunable sensing device 1 may be made by microelectromechanical systems (MEMS) techniques, in which the dielectric unit 3 and the electrode unit 5 are formed by techniques of etching, hole formation, etc., followed by disposing the tunable member 4 into the receiving space 35, and subsequently forming the covering layer 36 on the dielectric unit 3. The manufacturing techniques of sensing devices are well known in the art, and detailed descriptions thereof are not further described for the sake of brevity.

The tunable sensing device 1 may be used in robotics, portable apparatuses, touch screens, biomedical technologies, etc. Referring to FIG. 2, when in use, an external force (F) is applied to the top portion 33 of the dielectric unit 3, causing the second electrode 52 and the top portion 33 to be deformed so as to deform the tunable member 4. A signal change between the first and second electrodes 51, 52 is measured.

In certain embodiments, an assembly of the first and second electrodes 51, 52 and the tunable member 4 is a capacitor, and the tunable sensing device 1 is used as a capacitive touch sensor. When the second electrode 52 and the tunable member 4 are deformed, a distance between the first and second electrodes 51, 52 is changed, and therefore a capacitance change (i.e., the signal change) can be measured between the first and second electrodes 51, 52. It should be noted that the type of signal associated with the external force (F) applied to the tunable sensing device 1 may be a signal other than capacitance, such as resistance, optical property, etc. The type of signal is well known in the art and therefore is not further described for the sake of brevity.

It is known that capacitance is inversely proportional to the distance between the first and second electrodes 51, 52. When a larger amount of the external force (F) is applied, deformation of the tunable member 4 is increased, which moves the second electrode 52 and the first electrode 51 closer together, resulting in a larger capacitance between the first and second electrodes 51, 52. When the external force (F) exceeds the deformation limit of the tunable member 4, the tunable member 4 is no longer capable of being deformed, and thus a maximum capacitance value (i.e., saturation capacitance) is measured between the first and second electrodes 51, 52. In such case, capacitance greater than the saturation capacitance cannot be measured.

Referring to FIG. 3 in which the ER-fluid is exemplified as the tunable member 4, measuring capacitance greater than the saturation capacitance is possible by applying the external electric field to the tunable member 4 to adjust the stiffness of the tunable member 4. Specifically, in certain embodiments, the first electrode 51 is negatively charged, and the second electrode 52 is positively charged. The particles 42 of the tunable member 4 are polarized to align along the external electric field. When applying the external force (F) to the tunable sensing device 1, the polarized particles 42 of the tunable member 4 exert a resilient force (F_(r)) against the external force (F). As such, the stiffness of the tunable member 4 is increased. Therefore, a larger amount of the external force (F) can be applied to the tunable sensing device 1 and a greater capacitance can be measured. In other words, a maximum capacitance value measured between the first and second electrodes 51, 52 when the tunable member 4 is applied with the external electric field is different from (e.g., larger than) a maximum capacitance value measured between the first and second electrodes 51, 52 when the tunable member 4 is not applied with the external electric field. In certain embodiments, the tunable member 4 is the MR-fluid, and the sensitivity of the tunable sensing device 1 can be changed by applying the external magnetic field to the tunable member 4.

FIG. 4 is a diagram showing the external force applied to the tunable sensing device 1 shown in FIG. 3 versus capacitance value measured between the first and second electrodes 51, 52 when the external electric field is not applied (i.e., 0V) and when the external electric field (i.e., 1V and 10V) is applied to the tunable member 4. When the external electric field is not applied to the tunable member 4 or a smaller external electric field (1V) is applied to the tunable member 4, saturation capacitance is reached at an external force of 50 mN. In other words, sensitivity of the tunable sensing device 1 is in the range of 0 to 50 mN. When a larger external electric field (10V) is applied to the tunable member 4, saturation capacitance is reached at an external force of 90 mN. That is, sensitivity of the tunable sensing device 1 is increased to up to 90 mN.

It should be particularly pointed out that the signal measuring mechanism of this disclosure may be changed according to practical requirements. That is, the electrode unit 5 may be replaced by other measuring unit, such as piezoresistive, piezoelectric, magnetoresistive, inductive, paramagnetic, diamagnetic, optic measuring units, etc.

FIG. 5 illustrates the tunable sensing device 1 shown in FIG. 3 being used as a spring 61 in a triaxial accelerometer 6. A sensing mass member 62 is connected to the spring 61. Sensitivity of the triaxial accelerometer 6 is controllable by adjusting the stiffness of the spring 61.

Besides being used as a touch sensor or in the triaxial accelerometer, the tunable sensing device 1 may be applied to other MEMS systems, where a tunable sensing device is needed.

To sum up, with the tunable member 4 having the stiffness tunable by the external electric field or the external magnetic field, sensitivity of the tunable sensing device 1 is tunable without having to replace the dielectric member as in the conventional sensing device.

While the disclosure has been described in connection with what are considered the exemplary embodiment, it is understood that this disclosure is not limited to the disclosed embodiment and variation but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements. 

What is claimed is:
 1. A tunable sensing device, comprising: a substrate; a deformable dielectric unit that is disposed on said substrate, and that is formed with a receiving space; and a tunable member that is received in said receiving space, and that has a stiffness tunable by an external electric field or an external magnetic field.
 2. The tunable sensing device as claimed in claim 1, further comprising an electrode unit that includes a first electrode and a second electrode, which are disposed in said dielectric unit, and are respectively disposed at two opposite sides of said tunable member.
 3. The tunable sensing device as claimed in claim 2, wherein said tunable member includes an insulating fluid and a plurality of particles dispersed in said insulating fluid.
 4. The tunable sensing device as claimed in claim 3, wherein said particles of said tunable member are dielectric particles that are capable of aligning along the external electric field for increasing said stiffness of said tunable member.
 5. The tunable sensing device as claimed in claim 3, wherein said particles of said tunable member are magnetic particles that are capable of aligning along the external magnetic field for increasing said stiffness of said tunable member.
 6. The tunable sensing device as claimed in claim 2, wherein said tunable member is an electrorheological fluid.
 7. The tunable sensing device as claimed in claim 2, wherein said tunable member is a magnetorheological fluid.
 8. The tunable sensing device as claimed in claim 2, wherein said tunable member is an electroactive polymer.
 9. The tunable sensing device as claimed in claim 2, wherein a maximum capacitance value measured between said first and second electrodes when said tunable member is applied with the external electric field or the external magnetic field is larger than a maximum capacitance value measured between said first and second electrodes when said tunable member is not applied with the external electric field or the external magnetic field.
 10. The tunable sensing device as claimed in claim 2, wherein a maximum capacitance value measured between said first and second electrodes when said tunable member is applied with the external electric field or the external magnetic field is different from a maximum capacitance value measured between said first and second electrodes when said tunable member is not applied with the external electric field or the external magnetic field.
 11. The tunable sensing device as claimed in claim 2, wherein: said dielectric unit has a bottom portion disposed on said substrate, a side portion extending from a periphery of said bottom portion away from said substrate, and a top portion connected to said side portion and opposite to said bottom portion; said bottom portion, said side portion and said top portion cooperatively define said receiving space; and said first electrode is disposed in said top portion and said second electrode is disposed in said bottom portion.
 12. The tunable sensing device as claimed in claim 11, wherein said dielectric unit further has at least one through hole penetrating through said top portion, and being in spatial communication with said receiving space, and said dielectric unit includes a covering layer disposed on said top portion and covering said at least one through hole.
 13. The tunable sensing device as claimed in claim 12, wherein said top portion of said dielectric unit is formed with a recess in which said second electrode is disposed.
 14. The tunable sensing device as claimed in claim 12, wherein said covering layer is made of a material selected from the group consisting of parylene C, parylene D, parylene N, silicon dioxide, silicon nitride, polyimide, metal, and combinations thereof. 